An important purpose of detergents and/or cleaning compositions is to remove soils and stains from fabrics to achieve consumer perceivable cleaning benefit. The ability of a particular detergent or cleaning composition to remove soils and stains is determined not only by the surfactant activity level in the composition, but also by many others factors.
For example, the wash water used with detergents or cleaning compositions may contain various metal ions (e.g., calcium or magnesium ions) that can chemically combine with surfactants in the wash to form insoluble precipitates, which not only render the surfactant ineffective for soil/stain removal, but also form scums that further soil the fabric surface. Therefore, water with a higher concentration of metal ions (i.e., hard water) presents a particularly challenging wash condition. This challenge is further exacerbated by the recent change in consumers' laundering habits that are aiming at reducing energy consumption (e.g., by re-using wash water, such as re-using bath water for laundering) and improving environmental sustainability (e.g., by eliminating phosphate and/or zeolite builders and reducing total surfactant content in detergents) of the laundering processes. This brings additional challenges because re-used wash water tends to have harder (i.e., high concentrations of metal ions) and increased levels of soil contaminants, and elimination of phosphate and/or zeolite builder and reduction of total surfactant content in the detergent or cleaning compositions may lead to significant reduction in the cleaning performance.
Various polymers have been used in detergents or cleaning compositions in recent years as detergent builders in augmenting the cleaning power of surfactants. For example, some polymers can bind calcium ions and/or other alkali earth metal ions in water, thereby improving the water hardness tolerance of the detergents or cleaning compositions and allowing either elimination or significant reduction of conventional phosphate and/or zeolite builders in such compositions. Other polymers can effectively suspend soil particles (either inorganic or organic) that have already been removed from the fabric surface by surfactants, in the wash liquor and prevent their redeposition back onto the fabric surface during subsequent wash and rinse steps.
Water-soluble copolymers formed by polymerization of one or more monomers derived from unsaturated monocarboxylic acid, unsaturated polyalkylene glycol, and sulfonate group-containing hydrocarbons (such as those disclosed in Japanese Patent Application Publication Nos. JP2004-75977 and JP2010-111792A; U.S. Pat. No. 6,451,952 and U.S. Pat. No. 7,390,776) have demonstrated effectiveness as polymeric detergent builders. Specifically, JP2010-111792A discloses a group of copolymers containing structural units derived from sulfonate group-containing monomers, polyoxyalkylene monomers, and carboxylic acid monomers, which exhibited improved effectiveness in anti-soil redeposition and can be used in detergent or cleaning compositions to improve the overall cleaning performance thereof. However, there is still room for improvement in such polymers with respect to their anti-soil redeposition properties, and particularly their anti-redeposition properties against hydrophilic soils (such as clay) under high water hardness conditions.
There is a continuing need for a detergent or cleaning composition with superior cleaning performance than has existed before. In particular, there is a need for a detergent or cleaning composition incorporating water-soluble polymers with further improved anti-soil redeposition efficacy, especially anti-redeposition efficacy against hydrophilic soil under higher water hardness conditions. It would also be advantageous to provide laundry detergent compositions with improved fabric whiteness maintenance benefit after repeated wash cycles over extended periods of time. Further, it would be advantageous to provide liquid laundry detergent compositions with improved phase stability, i.e., exhibiting little or no phase separation over time even under environmental stresses imposed by harsh shipping conditions (e.g., elevated temperate and sun exposure).